Changes in Available-For-Sale Investments and Derivatives Classified as Level 3 (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 560		$ 5,057
Effect of change in accounting principle			(575)	[1]
Revised balance, beginning of period			4,482
Realized gains or losses included in earnings	(274)		84
Unrealized gains or losses included in other comprehensive income	0		142
Purchases	(6)		0
Sales	12		(765)
Settlements	248		(6)
Transfers into Level 3	3,643	[2]	956	[3]
Transfers out of Level 3	(380)	[4]	(4,333)	[5]
Balance, end of period	3,803		560
Change in unrealized gains (losses) still held	(272)	[6]	(30)	[7]
Fixed Maturities | Mortgage- and asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	267		62
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			62
Realized gains or losses included in earnings	(16)		(1)
Unrealized gains or losses included in other comprehensive income	18		20
Purchases	0		0
Sales	0		(3)
Settlements	(10)		(4)
Transfers into Level 3	139	[2]	237	[3]
Transfers out of Level 3	(4)	[4]	(44)	[5]
Balance, end of period	394		267
Change in unrealized gains (losses) still held	(16)	[6]	0	[7]
Fixed Maturities | Public Utilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0		497
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			497
Realized gains or losses included in earnings	0		0
Unrealized gains or losses included in other comprehensive income	0		(9)
Purchases	0		0
Sales	0		(2)
Settlements	0		0
Transfers into Level 3	422	[2]	0	[3]
Transfers out of Level 3	0	[4]	(486)	[5]
Balance, end of period	422		0
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Fixed Maturities | Collateralized Debt Obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	5		267
Effect of change in accounting principle			(263)	[1]
Revised balance, beginning of period			4
Realized gains or losses included in earnings	(2)		1
Unrealized gains or losses included in other comprehensive income	0		0
Purchases	0		0
Sales	(3)		0
Settlements	0		0
Transfers into Level 3	0	[2]	0	[3]
Transfers out of Level 3	0	[4]	0	[5]
Balance, end of period	0		5
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Fixed Maturities | Sovereign and Supranational
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0		293
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			293
Realized gains or losses included in earnings	0		0
Unrealized gains or losses included in other comprehensive income	0		5
Purchases	0		0
Sales	0		0
Settlements	0		0
Transfers into Level 3	434	[2]	0	[3]
Transfers out of Level 3	0	[4]	(298)	[5]
Balance, end of period	434		0
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Fixed Maturities | Banks/financial Institutions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	386		1,240
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			1,240
Realized gains or losses included in earnings	1		6
Unrealized gains or losses included in other comprehensive income	15		69
Purchases	0		0
Sales	0		(175)
Settlements	0		(2)
Transfers into Level 3	1,048	[2]	330	[3]
Transfers out of Level 3	(376)	[4]	(1,082)	[5]
Balance, end of period	1,074		386
Change in unrealized gains (losses) still held	1	[6]	0	[7]
Fixed Maturities | Other Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0		1,248
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			1,248
Realized gains or losses included in earnings	0		0
Unrealized gains or losses included in other comprehensive income	0		6
Purchases	0		0
Sales	0		0
Settlements	0		0
Transfers into Level 3	1,105	[2]	0	[3]
Transfers out of Level 3	0	[4]	(1,254)	[5]
Balance, end of period	1,105		0
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Perpetual Securities | Banks/financial Institutions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0		1,441
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			1,441
Realized gains or losses included in earnings	0		108
Unrealized gains or losses included in other comprehensive income	0		51
Purchases	0		0
Sales	0		(585)
Settlements	0		0
Transfers into Level 3	526	[2]	149	[3]
Transfers out of Level 3	0	[4]	(1,164)	[5]
Balance, end of period	526		0
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	4		9
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			9
Realized gains or losses included in earnings	0		0
Unrealized gains or losses included in other comprehensive income	0		0
Purchases	0		0
Sales	0		0
Settlements	0		0
Transfers into Level 3	0	[2]	0	[3]
Transfers out of Level 3	0	[4]	(5)	[5]
Balance, end of period	4		4
Change in unrealized gains (losses) still held	0	[6]	0	[7]
Derivatives | Interest rate swaps
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0
Realized gains or losses included in earnings	(33)
Unrealized gains or losses included in other comprehensive income	0
Purchases	0
Sales	0
Settlements	4
Transfers into Level 3	59	[2]
Transfers out of Level 3	0	[4]
Balance, end of period	30
Change in unrealized gains (losses) still held	(33)	[6]
Derivatives | Foreign currency swaps
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	241		0
Effect of change in accounting principle			0	[1]
Revised balance, beginning of period			0
Realized gains or losses included in earnings	(160)		1
Unrealized gains or losses included in other comprehensive income	(33)		0
Purchases	(6)		0
Sales	0		0
Settlements	(8)		0
Transfers into Level 3	(90)	[2]	240	[3]
Transfers out of Level 3	0	[4]	0	[5]
Balance, end of period	(56)		241
Change in unrealized gains (losses) still held	(160)	[6]	1	[7]
Derivatives | Credit default swaps
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	(343)		0
Effect of change in accounting principle			(312)	[1]
Revised balance, beginning of period			(312)
Realized gains or losses included in earnings	(64)		(31)
Unrealized gains or losses included in other comprehensive income	0		0
Purchases	0		0
Sales	15		0
Settlements	262		0
Transfers into Level 3	0	[2]	0	[3]
Transfers out of Level 3	0	[4]	0	[5]
Balance, end of period	(130)		(343)
Change in unrealized gains (losses) still held	$ (64)	[6]	$ (31)	[7]

[1] Change in accounting for VIEs effective January 1, 2010. See Notes 1, 3, and 4 for additional information.

[2] Due to a lack of visibility to observe significant inputs to price

[3] Due to a lack of visibility to observe significant inputs to price and credit events of respective issuers of securities

[4] A result of changing our pricing methodology to using a third party pricing vendor for estimating fair value instead of obtaining pricing of the securities from brokers or arrangers

[5] A result of changing our pricing methodology to using a pricing index for estimating fair value instead of obtaining pricing of the securities from brokers or arrangers

[6] Represents the amount of total gains or losses for the period, included in earnings, attributable to the change in unrealized gains (losses) relating to assets classified as Level 3 that were still held at December 31, 2011

[7] Represents the amount of total gains or losses for the period, included in earnings, attributable to the change in unrealized gains (losses) relating to assets classified as Level 3 that were still held at December 31, 2010